This article explores the newly catalogued manuscripts of the English Poor Clares preserved in Palace Green Library, Durham. It argues that the collection advances our understanding of the spirituality of the Poor Clares, a group who have received substantially less attention than their Benedictine and Carmelite counterparts. Focusing on manuscript evidence relating to mysticism at the convents of Aire and Rouen, it suggests three areas of interest to scholars of English women religious and recusant Catholic spirituality. First, it explores how a dual understanding of unio mystica in the convents converted wider concepts of anonymity and self-effacement into a radical form of authorial poverty. Through this, the nuns sought not only to unite with God but also achieve a symbolic union with each other. Secondly, it explores how the physical objects of the crucifix and Eucharist served to inspire a deeper mystical pattern of growth within the souls of the nuns. It suggests that feast days and specific times of the year, especially building up to Easter, had a profound effect on spiritual outpourings. Finally, the article explores the importance of the concept of the “heavenly Jerusalem” to the Poor Clares, revealing its centrality to their understanding of their life as a pilgrimage and their own lived experience as exiles.